Multiple pane insulating glass (IG) units or windows have been in use for many years. Over this time, many variations in window design have been made. Most designs involve two or more panes of glass which are held in a spaced relationship by a spacer which is located between the panes at their edges. The spacer and panes are typically fixed together by a sealant or other means. The spacer and panes thereby define a closed interior space in the insulating glass unit which is largely responsible for the insulating benefit associated with the unit.
Typically, when the IG unit is sealed, some water vapor remains in the resulting closed interior space. If no measures are taken, this water vapor would condense on the panes when the unit is exposed to typical service temperatures thereby causing fogging. A similar effect may occur if materials used to construct the IG unit contain volatile organic compounds which can pass to the interior space of the unit. To prevent fogging, most IG unit designs provide a means for adsorbing water vapor/chemical volatiles in the interior space over the expected life of the IG unit.
In conventional designs, one or more compartments are located at the periphery of the interior space either in the spacer itself or adjacent to the spacer. The compartment(s) is adapted to contain adsorbent materials (typically desiccants) in bead form in a manner such that the adsorbent beads communicate with the interior space to provide an adsorbing function for that space while the beads are retained in and by the compartment(s). Thus, fogging is prevented.
The beads used for this type of application generally consist of one or more types of molecular sieve bound by an inorganic binder (typically clay). The beads are designed to be free-flowing. Thus, they can easily be poured into the compartment to provide the desired quantity of desiccant.
While this basic IG technology has been for many years, the conventional clay-bound adsorbent beads present handling problems especially for the window manufacturer. Specifically, clay-bound adsorbent beads generally cause a large amount of dust. This dust is caused in part by the fact that clays are powdery materials by nature and also because the beads are susceptible to brittle crushing during handling which causes disintegration of the beads into dust.
The dust problem has been considered to be largely inescapable. The desire to avoid the problem has led to alternative designs which avoid the use of beaded desiccants use of desiccated adhesive resins which are adhered directly to the specially designed spacers and/or by use of special spacer constructions whereby the spacer is formed in part by a desiccated resin. These alternatives are expensive both from the point of raw materials cost and from the point of capital cost associated with the purchase of equipment needed to implement the alternatives.
Thus, there is a need for a solution to the dusting problem which still allows window manufacturers to use conventional IG unit designs and manufacturing equipment while avoiding the dust problem associated with conventional clay-bound beads.
There are similar needs for improved adsorbent beads to replace conventional inorganic-bound adsorbent beads in other applications.